Rare butterflies at Calstone and Cherhill Downs

Keith Steggall, National Trust Wiltshire Landscape Ranger Keith Steggall National Trust Wiltshire Landscape Ranger
Marsh fritillary butterfly

Chalk downland is home to some of our rarest butterflies.

Chalk downland is home to some of our rarest butterflies.  The chalk grassland flora provides the foodplants for the larvae of species such as Adonis blue which can be seen on the wing in May into early June and then a second brood at the end of the summer.  When freshly emerged the butterfly has a wonderful iridescence.  Marsh fritillary can be seen in late May into June, it has a beautiful chequerboard pattern.  The larvae of this butterfly can be seen in tent like webs on its foodplant, devils-bit scabious in late summer.  Other butterflies to look out for are common and small blue and brown argus from the same family and the wall brown which likes basking on bare chalk.  In July look out for the fast flying dark green fritillary and chalkhill blue with its paler blue colour.  More common is marbled white which has a very striking black and white pattern seen in the middle of summer.  Warm, sheltered spots are the best places to look, the coombes of Calstone Down is a top spot as is the steep south facing slope of the west end of Cherhill Down.  The ramparts around the Iron Age hill fort also provide a warmer micro-climate.